Hi Modeler#1,
I'm doing the same thing too as soon as I get my boat finished.
I'm going to the local RR store and picking up Woodland Senics Realistic water. It is a type of resin that is poured on layer by layer and hardens to look like water. It works, b/c when my sister was with me at the rr store, she thought it was just standing water.
here is an article on how to use clear casting resin to make water
just block the edges and pour it then remove when finished. It won't slosh around when the dio is disturbed.
I will do the same 
James